How old is the universe?

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It is currently thought that the universe is about 13.8 billion years old, give or take a few hundred million or even billion years. Astronomers and astrophysicists have come to this conclusion by looking at two types of evidence.

One method used is to estimate the age of the oldest stars. We have a pretty good idea of how long different-sized stars will burn. It appears that the oldest stars, known as globular clusters, have been around between eleven and fourteen billion years. However, this method of estimating the age of the universe is imprecise at best.

Scientists also consider the rate of the universe's expansion to estimate its age. By measuring the apparent rate of expansion and the movement of galaxies and comparing this to what is known as the Hubble constant, astrophysicists can extrapolate that this movement began almost around 13.77 billion years ago.

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